Platek-Mielczarek Anetta, Lang Johanna, Töpperwien Feline, Walde Dario, Scherer Muriel, Taylor David P, Schutzius Thomas M
Laboratory for Multiphase Thermofluidics and Surface Nanoengineering, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, Zurich CH-8092, Switzerland.
Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, Zurich 8092, Switzerland.
ACS Appl Mater Interfaces. 2023 Oct 18;15(41):48826-48837. doi: 10.1021/acsami.3c10680. Epub 2023 Oct 9.
Natural salinity gradients are a promising source of so-called "blue energy", a renewable energy source that utilizes the free energy of mixing for power generation. One promising blue energy technology that converts these salinity gradients directly into electricity is reverse electrodialysis (RED). Used at its full potential, it could provide a substantial portion of the world's electricity consumption. Previous theoretical and experimental works have been done on optimizing RED devices, with the latter often focusing on precious and expensive metal electrodes. However, in order to rationally design and apply RED devices, we need to investigate all related transport phenomena─especially the fluidics of salinity gradient mixing and the redox electrolyte at various concentrations, which can have complex intertwined effects─in a fully functioning and scalable system. Here, guided by fundamental electrochemical and fluid dynamics theories, we work with an iron-based redox electrolyte with carbon electrodes in a RED device with tunable microfluidic environments and study the fundamental effects of electrolyte concentration and flow rate on the potential-driven redox activity and power output. We focus on optimizing the net power output, which is the difference between the gross power output generated by the RED device and the pumping power input, needed for salinity gradient mixing and redox electrolyte reactions. We find through this holistic approach that the electrolyte concentration in the electrode rinse solution is crucial for increasing the electrical current, while the pumping power input depends nonlinearly on the membrane separation distance. Finally, from this understanding, we designed a five cell-pair (CP) RED device that achieved a net power density of 224 mW m CP, a 60% improvement compared to the nonoptimized case. This study highlights the importance of the electrode rinse solution fluidics and composition when rationally designing RED devices based on scalable carbon-based electrodes.
自然盐度梯度是一种很有前景的所谓“蓝色能源”来源，它是一种可再生能源，利用混合的自由能来发电。一种将这些盐度梯度直接转化为电能的很有前景的蓝色能源技术是反向电渗析（RED）。如果充分发挥其潜力，它可以提供世界电力消耗的很大一部分。之前已经开展了关于优化RED装置的理论和实验工作，后者通常侧重于昂贵的贵金属电极。然而，为了合理设计和应用RED装置，我们需要在一个功能齐全且可扩展的系统中研究所有相关的传输现象，尤其是盐度梯度混合的流体力学以及不同浓度的氧化还原电解质，它们可能会产生复杂的相互交织的影响。在这里，在基础电化学和流体动力学理论的指导下，我们在一个具有可调微流体环境的RED装置中使用基于铁的氧化还原电解质和碳电极，并研究电解质浓度和流速对电位驱动的氧化还原活性和功率输出的基本影响。我们专注于优化净功率输出，净功率输出是RED装置产生的总功率输出与盐度梯度混合和氧化还原电解质反应所需的泵送功率输入之间的差值。通过这种整体方法，我们发现电极冲洗溶液中的电解质浓度对于增加电流至关重要，而泵送功率输入非线性地取决于膜分离距离。最后，基于这一认识，我们设计了一个五电池对（CP）的RED装置，其净功率密度达到224 mW m CP，与未优化的情况相比提高了60%。这项研究突出了在基于可扩展的碳基电极合理设计RED装置时，电极冲洗溶液的流体力学和组成的重要性。
